Combined modality, radiation plus chemotherapy, studies will be undertaken using experimental tumors in mice in efforts to determine the feasibility and advantage of using the combined therapy in contrast to single modality therapy. Using tumors (initially a mouse mammary adenocarcinoma) that readily metastasize from subcutaneous implants, radiation therapy will be directed at the primary tumor, with or without surgical excision, while chemotherapy will be directed at both the local and regional tumors as well as the metastatic tumor. Prior to use of the combined approach, studies of the independent modalities will be undertaken to determine optimal dose-regimens and curative ability of each modality. The effects of drugs and X-irradiation on the tumor cell populations, intestinal epithelial crypt cells, and hemopoietic stem cells will be studied. Finally, the two modalities will be employed in combination, simultaneously and sequentially, for determination of optimal dose-regimen and time-sequence parameters. When evidence of developing drug resistance becomes apparent, combinations of effective chemotherapeutic agents will be used.